1. Field of the Invention
The invention relates to a device for filtering a liquefied plastic material. More particularly, the invention relates to a device having a plurality of filters and filter chambers. More particularly yet, the invention relates to a device that enables cleaning of a filter without interrupting the production process.
2. Description of the Prior Art
A conventional device is described in DE 102 54 022 B4. The device described in this prior art reference is based on prior art, for example, according to EP 0 798 098 B1.
In the case of the known device according to EP 0 798 098 B1, at least two filter elements are arranged in the flow path of the liquid in corresponding filter chambers. The filter chambers are arranged on a filter slide that is movably positionable transverse to the flow direction. On the filtered side of the filter, a single connecting channel is provided, so as to hydraulically connect the filtered side of the two filter elements with each other.
This arrangement requires a long housing and a long filter slide bolt, and, thus, also a longer slide path. A longer slide path, in turn, requires a larger hydraulic cylinder arrangement and a sturdier design for all components that are connected to the hydraulic arrangement.
The conventional device disclosed in prior art reference DE 102 54 022 B4 is an attempt to achieve the largest possible filter surface with the smallest possible filter slide diameters. This object, which was the basis for the known device, is achieved by providing two filter-slide split channels in the filter slide for each filter chamber on the clean side of the filter. These split filter channels open from the filter chamber into the discharge channel.
Furthermore, the actual discharge channel is also divided into four housing split channels. Both the production position and the backflow position are realized in this device. The filter chamber may then be so adjusted by sliding the filter slide, so that a flow path is blocked from the filter chamber to the discharge channel and the backflow channel. This configuration of the filter results in an increase in pressure in the blocked filter chamber, which results in improved backflow.
It is apparent that this device achieves its aim, but is expensive to produce.
WO 2004/026432 A1, FIG. 10ff. disclose a device for filtering a liquid, particularly for apparatus that process plastic material. In this device, the feed channel is divided into a total of four split feed channels. This arrangement also enables a production position as well as a backflow position. By sliding the filter slide, it is possible to adjust the filter chamber so that the flow path is blocked between the filter chamber and the feed channel and the backflow channel. This configuration increases the pressure in the filter chamber, which results in improved backflow. This object is achieved, however, with a relatively long housing and, thus, also a relatively long filter slide. The slide path is consequently longer, which requires a larger hydraulic cylinder unit and more robustly built components that are used with such an hydraulic configuration.